Bleach has a pH of 13; is it considered an acid or a base?

The Short Answer

Bleach is definitely a base. In chemistry, any substance with a pH level greater than 7 is classified as alkaline or basic. Since bleach sits at a pH of approximately 13, it is considered a strong base.

Understanding the pH Scale

The pH scale is a measure of how acidic or basic a water-based solution is. The scale typically ranges from 0 to 14:

• pH < 7: The substance is an acid. Acids are characterized by a high concentration of hydrogen ions.

• pH = 7: The substance is neutral. Pure water is the classic example of a neutral substance.

• pH > 7: The substance is a base (or alkaline). Bases have a low concentration of hydrogen ions and a high concentration of hydroxide ions.

Comparison: Acids vs. Bases

To help you visualize the differences, refer to the table below:

Feature	Acids	Bases (Alkaline)
pH Range	0 to 6.9	7.1 to 14
Taste	Sour	Bitter
Texture	Often stinging	Slippery or soapy
Common Example	Lemon juice	Bleach, Baking soda

Why is Bleach a Strong Base?

Bleach (specifically sodium hypochlorite) is highly caustic. Because it has a pH of 13, it is very far from the neutral point of 7. This high alkalinity is exactly what makes bleach effective at breaking down organic stains, grease, and germs. However, this same strength is why you must handle it with extreme care; it can cause chemical burns to skin and damage to various surfaces.

Common Pitfalls

One common mistake is assuming that because a substance is a "strong cleaner," it must be an acid. While many industrial cleaners are acidic (like toilet bowl cleaners), many others—like bleach and oven cleaners—are powerful bases. Always remember: pH is a measure of chemical nature, not cleaning strength.

Another pitfall is mixing chemicals. Never mix bleach with acidic cleaners (like vinegar or ammonia). Because bleach is a strong base, mixing it with an acid causes a rapid chemical reaction that can release toxic, potentially lethal gases.